Alchemist Forseti ADP20 schematics

Basill · 25th October 2009, 10:36 AM

Hi,
I have decided to try to decipher the Alchemist Forseti Power Amp ADP20, from some photos found in the net

. Below I attatch the schematic I have made. I would appreciate any help in finding any mistakes. Originally it worked in class AB it had 153W in to 8ohms, i don't know if the power voltage 36V that i had counted is OK. So I need your help for this project

.

Basill · 26th October 2009, 06:02 PM

There isn't anyone to help me

?

ROLIKOV · 29th August 2010, 04:35 PM

Hello bassil

I have the same amplifier : ADP20 - MK2
I have now replaced all the output drivers , and need to tune the bias current .
Do you have any idea , how should i do it ?

Thanks

Enkie · 11th February 2011, 09:03 PM

For reference:

First, thanks for the schematic

However I think T13, T15 and T17 should have their base connections similar to T11.

A bit odd design regarding the driverstage, since it seems to be single ended. Very long time ago since I worked with those produces.

If I recall correct supply voltage is around +/- 55VDC, I dont have any figures of quiescent current - but pretty high. Approx 50mA for each transistor. Best place to measure is over a resistor in the PSU separating different capacitorbanks. 0.47ohm 5W or something like that I think it is.

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26th October 2009, 06:02 PM	#2
Basill diyAudio Member Join Date: Apr 2007	There isn't anyone to help me ?

29th August 2010, 04:35 PM	#3
ROLIKOV diyAudio Member Join Date: May 2007	Hello bassil I have the same amplifier : ADP20 - MK2 I have now replaced all the output drivers , and need to tune the bias current . Do you have any idea , how should i do it ? Thanks

11th February 2011, 09:03 PM	#4
Enkie diyAudio Member Join Date: Feb 2011	For reference: First, thanks for the schematic However I think T13, T15 and T17 should have their base connections similar to T11. A bit odd design regarding the driverstage, since it seems to be single ended. Very long time ago since I worked with those produces. If I recall correct supply voltage is around +/- 55VDC, I dont have any figures of quiescent current - but pretty high. Approx 50mA for each transistor. Best place to measure is over a resistor in the PSU separating different capacitorbanks. 0.47ohm 5W or something like that I think it is.

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